The higher data transfer rate as well as the higher integration degree and the higher density of the semiconductor integrated circuit device is requested nowadays. For this reason, an insulating film having a low dielectric constant with a small RC delay time (referred to as a “low-dielectric insulating film” hereinafter) is employed.
In case the low-dielectric insulating film is employed as an interlayer insulating film to cover the Cu wiring, it is possible that, because such low-dielectric insulating film is porous, Cu is ready to diffuse and thus reduction in the insulating property is brought about. Therefore, an insulating film for preventing the diffusion of Cu (referred to as a “barrier insulating film” hereinafter) is often employed between the low-dielectric insulating film and the Cu wiring.
The low-dielectric insulating film is formed as a porous film by the plasma CVD method using a film forming gas containing a silicon-contained organic compound and N2O, and then applying the O2 plasma process, or the like. Also, the barrier insulating film is formed by the plasma CVD method using the film forming gas containing the silicon-contained organic compound and N2O. Otherwise, in order to further improve the barrier characteristic of the formed film against the diffusion of Cu, such barrier insulating film is formed by the plasma CVD method using the film forming gas in which N2, NH3, etc. are added to the silicon-contained organic compound and N2O.